DENVER— Beads and flour could help explain a rare and mysterious phenomenon: lightning strikes called earthquake lights that occur before or during major quakes. New results presented March 6 at an American Physical Society meeting demonstrate that shifting granular materials, which simulate earth along a fault, can induce remarkably high electric voltages.

A few years ago, physicist Troy Shinbrot of Rutgers University in Piscataway, N.J., developed a simple experiment to determine whether ear...